1. Field of the Invention
The present invention relates generally to an ink-jet printing apparatus electrically connecting a head on a carriage and a printing circuit board in a main body of the apparatus by means of a flexible wiring board. More particularly, the invention relates to an ink-jet printing apparatus for large size printing, in which a motion distance of the carriage is long.
2. Description of the Related Art
As one kind of prior art, an ink-jet printer will be briefly explained with reference to FIGS. 12, 13 and 14.
FIG. 12 is a top plan view of a conventional ink-jet printer, FIG. 13 is a front elevation of the conventional ink-jet printer and FIG. 14 is a section taken along line K--K of FIG. 13. In the ink-jet printer illustrated in these figures, an ink is supplied from an ink tank 8 to a head through a tube 4. The tube 4 has an intermediate curved portion and is connected to a head 1 through a caterpillar 2 which protects and supports the tube.
Namely, the caterpillar 2 is respectively fixed to the main body of the printer and a carriage at both ends and provided with flexibility so as to follow to motion of the carriage 6.
On the other hand, a head 1 and a main board 30 constituting a control board of the printer are electrically connected by a flexible wiring board 3, which is in a form of the flat plate, formed by coating a plurality of conductors with a resin. By this, electrical signals are fed from the main board 30 to the head 1, ejection of the ink by the head can be controlled. The flexible wiring board 3 is loosely supported by a plurality of displacement restricting members 5 mounted on the caterpillar 2. By this, upon shifting the carriage 6 in directions of arrow I shown in FIG. 12, the flexible wiring board 3 can be deformed to curve with a predetermined bending radius together with the caterpillar 2. It should be noted that motion of the carriage 6 is enabled by transmitting a driving force of a carriage motor 10 via a belt 7.
As shown in FIG. 14, a printing paper sheet 13 is fed in a direction shown by arrows G and H in FIG. 14 by a paper feeding roller 17 and a subscanning roller 9. During feeding of the paper sheet, ink is ejected on the printing paper sheet from the head 1 to perform printing.
Next, a construction of the foregoing caterpillar 2 will be explained with reference to FIGS. 15, 16, 17, 18 and 19.
FIG. 15 is a front elevation of the caterpillar 2, in which the tube 4 is received, FIG. 16 is a top plan view of the caterpillar 2 illustrated in a condition where the tube 4 is received, FIG. 17 is a section taken along line L--L of FIG. 15, FIG. 18 is a front elevation showing a component of the caterpillar 2, and FIG. 19 is a top plan view of a component shown in FIG. 18.
The caterpillar 2 is constructed by connecting a plurality of components of substantially U-shaped cross-section shown in FIGS. 18 and 19. Mutual connection of the components becomes possible by rotatably engaging shafts 19 with holes 20 of other components 21. By connecting a plurality of components 21, the caterpillar 2 shown in FIGS. 15 and 16 can be formed. As set forth, the components 21 are pivotable relative to each other about the shafts 19 and the holes 20. Thus, the caterpillar 2 is formed into a polyarticular link structure. As a result, in FIG. 15, when a force in a direction N is exerted at a portion M, a portion O of the caterpillar 2 with a curved portion of the predetermined curve radius is shifted to a portion Q which is shown by a broken line.
Next, a support structure of the flexible wiring board 3 will be explained hereinafter with reference to FIGS. 20, 21 and 22.
FIG. 20 is an enlarged illustration of a portion J of FIG. 13, FIG. 21 is a top plan view of the portion J shown in FIG. 20, and FIG. 22 is a section taken along line M--M of FIG. 20. As shown in FIG. 22, the flexible wiring board 3 is loosely held in a displacement restricting member 5 having a substantially rectangular cross section. The flexible wiring board 3 is inserted into the displacement restricting member 5 by deflecting an engaging leaf spring 16 forming one side of the displacement restricting member 5 to open the displacement restricting member 5. Particularly, when a distance to move the carriage 6 is long, it becomes necessary to support the flexible wiring board 3 so as not to deflect downwardly. Then, the displacement restricting member 5 is engaged by fitting a mounting projection 14 on a side piece of the displacement restricting member mounting member 11 having a substantially U-shaped configuration. On the other hand, the displacement restricting member mounting member 11 is coupled with a caterpillar mounting member 18 mounted on the caterpillar 2 by means of screws 15. With such construction, the flexible wiring board 3 is constructed to be deformed to curve together with the caterpillar 2.
In the conventional ink-jet printer set forth above, since the displacement restricting member 5 is formed of a material having low sliding ability, when the flexible wiring board causes curving deformation associated with movement of the head, a sliding load by the displacement restricting member 5 relative to the flexible wiring board 3 becomes relatively large. In the alternative, when the flexible wiring board 3 is fixed to the displacement restricting member, a reaction force due to flexural rigidity of the flexible wiring board 3 becomes large for not escape margin of the flexible wiring board 3.
On the other hand, since the component of the caterpillar 2 is formed of a material having high frictional property, a sliding resistance with the component of the caterpillar 2 upon curving deformation of the tube associated with movement of the head, becomes large. As a result,
1. A driving load of the carriage becomes large to require large driving force of the carriage driving motor 10 to make a cost of the carriage motor high. PA0 2. With relative sliding motion of the flexible wiring board 3 and the displacement restricting member 5, the flexible wiring board 3 is worn to cause breakage. PA0 3. By slidingly contacting the tube 4 with the caterpillar 3, the tube is worn to cause rapture in the tube 4.
Moreover, in the conventional ink-jet printer, the curve radius of the flexible wiring board 3 is substantially the same as the curve radius of the caterpillar 2. As set forth above, the displacement restricting member 5 is frequently mounted on the side portion along the caterpillar 2. As a result, the displacement restricting member 5 thus mounted hinders down-sizing of the overall apparatus.
Furthermore, in the conventional ink-jet printer, the flexible wiring board 3 is movably constructed with respect to respective of the carriage 6 and the body of the apparatus in the coupling portion between the carriage 6 and the caterpillar 2 and in the coupling portion between the body of the apparatus and the caterpillar 2. As a result, the flexible wiring board 3 may be offset with respect to the carriage 6 or the body of the apparatus to cause a breakage in the flexible wiring board 3.